1. Field of the Invention
The present invention relates to an engine generator unit including an engine and an electric-power generator driven by the engine.
2. Related Prior Art
Among general-purpose power supply devices suitable for use outdoors is the so-called engine generator unit which includes an engine and an electric-power generator driven by the engine. During operation, the engine, generator and muffler in the engine generator unit tend to become hot and thus are normally cooled via a cooling fan device. Typical examples of such an engine generator unit are shown in Japanese Utility Model Publication Nos. HEI-3-6831 and HEI-4-42494 and Japanese Patent Publication No. HEI-3-79532.
In the engine generator unit disclosed in Japanese Utility Model Publication No. HEI-3-6831, outside air is introduced into a space defined by the engine shroud, by means of a cooling fan device attached to the engine, in order to cool the engine cylinder and its vicinity. The outside or cooling air having cooled the engine cylinder is then passed through an exhaust air guide and blown onto the muffler while cooling an exhaust manifold, to thereby lower the temperature of the muffler. On the other hand, the outside air is also introduced into the generator by means of another cooling fan device attached thereto in order to cool the interior of the generator.
The engine generator unit disclosed in the No. HEI-4-42494 publication has a cooling fan device fixed to the engine, via which outside air is introduced into first and second cooling-air passages so that the engine cylinder is cooled by the air passing through the first cooling-air passage while the crankcase is cooled by the air passing through the second cooling-air passage. The air having cooled and passed the crankcase is then directed to cool the muffler.
Further, in the engine generator unit disclosed in the No. HEI-3-79532 publication, outside air is introduced, by means of a cooling fan device fixed to the engine, to cool both the engine and the generator, and the air having cooled and passed the engine and generator is directed to an exhaust air duct so as to cool the muffler provided within the exhaust air duct.
However, the first-mentioned prior engine generator unit disclosed in the No. HEI-3-6831 publication would require a great amount of cooling air in order to effectively cool the muffler because the muffler is cooled here by the cooling air after having passed the engine and hence having got relatively hot. Thus, arrangements must be made, in this unit, for directing as much cooling air as possible to the muffler with minimum leakage and for causing the cooling air to efficiently contact the muffler over the entire outer surface thereof. This is also the case with the second-mentioned prior engine generator unit. Further, the last-mentioned prior engine generator unit disclosed in the No. HEI-3-79532 publication would require a complicated cooling-air passage structure because of the arrangement that a great amount of the cooling air having passed the engine and generator is collected together and then directed to flow through the exhaust air duct.